Polymerized rosin is resin that is produced by polymerization of rosin such as gum rosin, wood rosin, or tall oil rosin. Polymerized rosin and derivatives such as polymerized rosin ester compounds have a high level of pigment dispersing ability, compatibility, cohesion and adhesion, and other properties, and therefore are advantageously used as binders or additives in a wide variety of fields such as printing ink, paint, pressure-sensitive adhesives or adhesives, and flux.
A variety of methods have been conventionally studied for producing polymerized rosin. There have been proposed, for example, a method using, as a catalyst, a polymer having pendant sulfonic acid groups (see Patent Document 1), and a method using aliphatic sulfonic acid as a catalyst (see Patent Document 2). There is also a well-known method that includes subjecting rosin acid to a polymerization reaction in an organic solvent such as toluene or xylene using, as a catalyst, an acidic compound such as formic acid, p-toluenesulfonic acid, methanesulfonic acid, hydrogen fluoride, zinc chloride, aluminum chloride, or titanium tetrachloride and removing the catalyst, the solvent, and the unreacted rosin after the reaction is completed, so that polymerized rosin is obtained.
In recent years, for global environment protection, alternatives to petroleum resources have been studied, and a variety of natural resources receive attention. Rosin, which can be obtained from turpentine, is a naturally-occurring material containing resin acids such as abietic acid and pimaric acid. Among the resin acids, abietic acid is known to be used as a material for polymers. For example, polymers obtained by polymerization of abietic acid and polyhydric alcohols are known (see Patent Document 3).